NCLDVs
The asfarviruses, iridoviruses, mimiviruses, phycodnaviruses and poxviruses have been shown to belong to a single group. - the large nuclear and cytoplasmic DNA viruses. These are also abbreviated "NCLDV". This clade can be divided into two groups:
- the iridoviruses-phycodnaviruses-mimiviruses group. The phycodnaviruses and mimiviruses are sister clades.
- the poxvirus-asfarviruses group.
It is probable that these viruses evolved before the separation of eukaryoyes into the extant crown groups. The ancestral genome was complex with at least 41 genes including (1) the replication machinery (2) up to four RNA polymerase subunits (3) at least three transcription factors (4) capping and polyadenylation enzymes (5) the DNA packaging apparatus (6) and structural components of an icosahedral capsid and the viral membrane.
The evolution of this group of viruses appears to be complex with gene having been gained from multiple sources.
Read more about this topic: DNA Virus